What began with Victoria's Secret stores in the US may soon be coming to a WAN near you. Since the late 1990s, high-traffic Web sites have used CDNs (content delivery networks) from companies such as Akamai Technologies and Digital Island to handle peak loads and special events such as the Victoria's Secret webcasts. Service providers, too, have long supported the technology, investing heavily in caching hardware and software that helps manage bandwidth utilisation within their networks.
But with the decline of ISPs, the dot-com bust, the reluctance of large media companies to put their content online, and most importantly, a wave of bandwidth-intensive business applications, attention is now shifting to content delivery in the enterprise.
Many companies now use CDNs to push traditional static content, frequently accessed data and large files (for example, PDF documents, streaming video, e-learning applications and corporate presentations) closer to the edges of their networks where they can be more easily accessed by end-users. Other companies have begun deploying CDN technology to deliver dynamic, database-driven content for business software such as ERP and CRM.
CDNs promise faster application performance and higher network availability. Couple that with the growing telecommuting trend and the rise in Net-enabled business services, and it's no wonder companies are mulling over the possibilities of edge networking.
Building a better network
A typical CDN consists of a group of servers, caches and routing software capable of moving frequently used content closer to end-users, thus maximising bandwidth efficiency and boosting network scalability and availability.
"It's essentially a store-and-forward mechanism that relies on repeat access to generate enhanced performance," says Neal Goldman, an analyst for The Yankee Group.
To understand how an enterprise CDN works, imagine the architecture of a public CDN such as Akamai, which relies on 13,000 servers (caches) located in data centres and ISPs around the world. The network uses a "pull-based" mechanism to keep local caches primed with the most frequently requested content.
For example, when a Web surfer connected to an ISP in Manchester clicks on a photo of England striker David Beckham on CNN.com's Web site, the photo is "pulled" to the Akamai server closest to that user's ISP. Anyone else in the network who subsequently requests Beckham's photo gets it from the same cache, rather than CNN's origin server, thus cutting down on bandwidth and eliminating router hops. Meanwhile, infrequently accessed content and content that has passed its "time-to-live" freshness date are regularly flushed out of the network.
And there's more: CDNs can also monitor network conditions to calculate optimal routing, minimise packet loss, balance network loads and provide route-around and fail-over capabilities.
Of course, in the enterprise the challenge is a bit different. Although the environment behind the firewall may be more predictable, and the universe of potential users better known, ECDNs (enterprise CDNs) must also provide more controlled distribution of content because the consequences of network disruption within a company are greater than on the public Internet.
As with a public CDN, an ECDN consists of load balancers, caches and proxies, all coordinated by a single software system. Typically, an enterprise will also deploy management tools to control the content flowing across the network. Publishing tools can interface with content management systems to inject the appropriate content into the network, such as material in the correct language for a particular geographical region. Bandwidth management tools allocate scarce WAN bandwidth among various users and applications. Routing tools set cache hierarchies so that, for example, if a file is not found in Kuala Lumpur, the system can check for it in Tokyo. Security and access tools restrict access to certain users or until certain times. And monitoring and reporting tools oversee who is using what and bill bandwidth costs to the right departments.
Things gets tricky when you try to distribute live video, which typically consumes a huge amount of network capacity. Given that most Web video is delivered using real-time streaming protocols such as RealVideo or Windows Media, the process of pushing that content efficiently to the edge of the network requires special software proxy caches that can "multicast", or receive, one copy from the origin server and pass it along to multiple simultaneous viewers.
This approach enables wider distribution than unicasting, which broadcasts all streams directly from the origin server. For example, Steve Jobs' latest Macworld keynote webcast topped out at 16.5Gbit/sec and was served simultaneously to a total of 80,000 users. Without multicasting, that would not be possible.
Alternatively, enterprises can address the challenge of live video by offering it on-demand, thus flattening the demand curve and making the content easier to cache. How effective is that strategy? Jim Ni, director of product management at CDN vendor F5 Networks, thinks that on-demand distribution will eventually be an effective substitute for live distribution.
"After the second CEO webcast, the guys in Singapore aren't going to wake up [in the middle of the night] to watch it live [anymore]," Ni predicts.
The City of San Diego is a case in point. San Diego now distributes all its city council meetings via webcast, using an ECDN from Network Appliance to also deliver the videos on-demand. Fire and police training videos, as well as videos of the city's sewer system for maintenance personnel, are also available.
To Allen Myers of the city's data processing group, San Diego's ECDN makes sense because it relieves the city's network of gargantuan video files from what would otherwise be a drag on response times. And as more business-related video and voice technologies come online, the need for ECDNs is only going to increase. "You're going to suck up the bandwidth with the next generation of apps real quick," Myers says.
With each passing day, public and corporate Web content becomes more and more dynamic or database-driven. At the same time, the distributed computing revolution rolls on. In response to both of those trends, CDN and ECDN vendors have begun developing techniques to enable the caching of dynamic page elements and, in some cases, even applications.
For example, a group of vendors including Akamai, Oracle and BEA Systems has introduced a markup language called ESI (Edge Side Includes) that enables edge servers to recognise, cache and render specially tagged dynamic content or perform data transformations at the edge of the network, based on various environmental variables.
"I could look at a user's cookie at the edge of the network, note that they're a Libra and deliver that horoscope," explains Kieran Taylor, director of product marketing at Akamai. "Without ESI, a single piece of dynamic content on the page renders the page uncachable."
Other vendors, such as F5 Networks and Network Appliance, have developed their own ESI-like algorithms. But with some industry leaders, such as Cisco and Microsoft, conspicuously absent from the ESI parade, it leaves open the question of which standard will benefit from the heavyweights' support.
Furthermore, to improve the performance of browser-based applications (such as ERP and CRM systems) from remote offices, vendors are working on software that can identify and serve as much of the presentation layer and underlying data as possible from the edge.
"The end-user thinks the application is slow, but it's really the network," observes F5's Ni. "The first baby step is to take the 100K bitmaps and [cache] them out there [on the edge]."
Other ECDN vendors claim they already support not only the caching of XML constructs while holding the session with a remote database, but even on-the-fly transformation for wireless formats.
It's all part of a return to rich-client computing, according to industry watchers such as The Yankee Group's Goldman, who predicts a rise in locally empowered applications and clients with data and application logic, as well as a built-in presentation policy. "[The CDNs] have to be able to deliver code at the edge," he says.
In a year or two, CDNs may even be able to deliver JavaServer Pages (JSPs), VBScript, Active Server Pages (ASPs) and possibly Enterprise JavaBeans (EJBs). "And the more the network is distributed across multiple peers, the more complex management and monitoring becomes," Goldman adds.
These developments put ECDN vendors on a convergence course with the storage world. "One of these large branch office caches can have two gigabytes of storage," notes Amit Pandey, senior marketing director at Network Appliance, which also sells storage. "That looks to me more like a file server."
The Call of Outsourcing
For various reasons, enterprises large and small are feeling a tug towards network management outsourcing - although most are just experimenting in a market that many still label as "immature".
Currently dominating the space are MSPs (managed service providers), which have been hampered recently by sagging revenues and customer confusion. But mighty telecoms and systems integrators are charging into the MSP market - a move likely to change market dynamics.
Yet the network outsourcing market is seeing "a fair amount of activity", as businesses get comfortable with the idea of handing over some network management duties. "I don't think outsourced services are just a middle-market play," says Mike Twomey, vice president of channels and business development at Tivoli, a software supplier to MSPs. "Enterprise customers will choose to outsource certain elements of their business too."
There is a commonality among the tasks users settle on in taking the plunge. At first, they're likely to start with tasks that are small, simple and well-boxed. Those functions might include managed firewalls, managed VPNs (virtual private networks) or managed WANs. Users also cite monitoring services and LAN management as natural first candidates for outsourcing.
At issue is the fact that "MSP" can describe a host of vendors; the label is applied to those that remotely manage infrastructures kept physically within an enterprise, as well as vendors hosting networking tasks in an outside data centre. IT managers must often sort out the nuances to determine which best meets their needs.
Most MSP users indicate that outsourced security and storage services are likely candidates for further network outsourcing, although those plans hinge on company strategy and the economy.box: Who's in the CDN gameFinally, a raft of startups is emerging to build the next generation of edge-delivery technology - always an encouraging sign for an emerging technology. From low-cost, peer-to-peer architectures (such as those marketed by Kontiki and CenterSpan), dynamic content caching solutions (Xcache Technologies, Chutney Technologies and SpiderSoftware), and packet-level caching systems (Expand Networks), to "pre-fetching" tools (Fireclick), "difference send" accelerators (FineGround Networks and Speedwise) and WAN management solutions (NetReality, Response Networks and NetScout), there's no shortage of innovative thinking these days - as long as you don't mind living on the edge.
Content delivery networks for the enterpriseContent delivery technology, born on the public Internet to help Web sites handle peak loads and improve performance, is now moving into the enterprise. Enterprise CDNs help firms distribute bandwidth-intensive content, such as rich media, throughout a WAN - especially to remote offices with low-bandwidth connections. The new networks consist of servers, caches, routing software and a host of management capabilities (including bandwidth allocation, content publishing, security, tracking and reporting). The next phase in ECDN development, already under way, will have the ability to deliver dynamic, database-driven content and improve application performance at the edge.